Surface Deposition of Nanoparticles During Pool Boiling of Nanofluids and Its Effects on CHF Enhancement Using Nanofluids

2007 ◽  
Author(s):  
Hyung Dae Kim ◽  
Moo Hwan Kim
Keyword(s):  
Tio2 Nanoparticles ◽  
Pool Boiling ◽  
Surface Wettability ◽  
Heater Surface ◽  
Surface Deposition ◽  
Nanoparticle Deposition ◽  
Water Based ◽  
Enhanced Surface ◽  
Capillary Wicking ◽  
Horizontal Wire

This paper is concerned about mechanism of outstanding CHF enhancement phenomena using nanofluids, a subject with academically and industrially remarkable interest. Pool boiling experiments using an electrically heated horizontal wire were carried out with various water-based nanofluids containing Ag, Al2O3, SiO2, and TiO2 nanoparticles. The results showed that nanoparticle deposition on the heater surface occurred during pool boiling of nanofluids, and that the effect of nanoparticle porous layer on CHF could explain enough the CHF enhancement of nanofluids. Then the porous surface was characterized using surface wettability and capillary wicking performance, which are the significant properties of boiling surface influencing CHF. Discussion of the results suggested that the outstandingly enhanced CHF performances of nanofluids under the nucleate pool boiling were associated with enhanced surface wettability and liquid suction effect due to capillary wicking on the nanoparticle-deposited surface.

Experimental Investigation of Critical Heat Flux Enhancement by Micro/Nanoscale Surface Modification in Pool Boiling

2008 ◽  
Author(s):  
Seontae Kim ◽  
Hyungmo Kim ◽  
Hyung Dae Kim ◽  
Ho Seon Ahn ◽  
Moo Hwan Kim ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Modification ◽  
Critical Heat Flux ◽  
Pure Water ◽  
Pool Boiling ◽  
Working Fluid ◽  
Nanoparticle Deposition ◽  
Structured Surfaces ◽  
Static Contact ◽  
Capillary Wicking

Nanofluids, which contain uniformly and stably dispersed nanoparticles, exhibit an abnormal enhancement of the critical heat flux (CHF) when used as a working fluid in pool boiling. It has recently been demonstrated that optimal CHF enhancement in nanofluids is attained by the significant deposition of nanoparticles on the heater surface during pool boiling. The surface deposition of oxidized metal nanoparticles significantly enhances the wettability, and fractal micro/nanostructures formed by nanoparticle deposition induce liquid suction due to capillary wicking. It is supposed that the superior wettability and capillary wicking of the nanoparticle-fouled surface enhances CHF by promoting the dry patches to be effectively rewetted during the boiling process. In this regard, the excellent CHF performance of the nanoparticle-deposited surface can be reproduced using artificial structures via innovative surface-modification methods that yield good wettability and capillarity. To accomplish this goal, we plan to design and fabricate various artificial micro/nano-structured surfaces with good surface wettability and capillarity, and investigate their CHF performance. In the present study, we examined experimentally the CHF performances of a series of surface-modified samples (plane, micro-structured, nano-structured, and micro/nano structured surfaces). Pool boiling heat transfer of pure water on sample surfaces was investigated under atmospheric conditions. The CHF increase due to artificial surface modification is discussed based on solid-liquid interfacial parameters (static contact angle, roughness) that are closely related to CHF phenomenon in pool boiling.

CONTROL OF POOL BOILING HYDRODYNAMICS THROUGH SURFACE WETTABILITY PATTERNING

2018 ◽  
Author(s):  
Taylor P. Allred ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Pool Boiling ◽  
Surface Wettability

Pool Boiling Characteristics of Metallic Nanofluids

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
K. Hari Krishna ◽  
Harish Ganapathy ◽  
G. Sateesh ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boiling Heat Transfer ◽  
Volume Fraction ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Solid Particles ◽  
Heater Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well.

New nanofluids, based on clay minerals, as promising heat carriers for energetics

Clay Minerals ◽  
2018 ◽  
Vol 53 (2) ◽  
pp. 255-269 ◽  
Author(s):  
Vasily Moraru
Keyword(s):  
Heat Transfer ◽  
Clay Minerals ◽  
Sudden Onset ◽  
Heater Surface ◽  
Enhancement Of Heat Transfer ◽  
Nanoparticle Deposition ◽  
Boiling Crisis ◽  
Transfer Parameters ◽  
Automated Installation ◽  
Heat Carriers

ABSTRACTIn an automated installation powered by direct current (DC), the boiling curves and heat-transfer-coefficient (HTC) dependencies on the superheat values (ΔT) under free convection conditions for the water nanodispersions of clay minerals – illite, montmorillonite, palygorskite and genetic mixtures of the latter two – were obtained. The effects of some factors on pool boiling heat transfer were also studied.A significant influence of the shape and anisotropy of nanoparticles (NPs) on the heat-transfer parameters of nanofluids (NFs) was detected. A significant critical heat flux (CHF) enhancement (up to 200–300%) at boiling of the nanofluids studied was established, which is due to nanoparticle deposition on the heater surface during nanofluid boiling. The structure of the nanomaterials deposited is important in the enhancement of heat transfer at boiling of nanofluids and in avoiding boiling crises.The present study showed the effectiveness of clay-mineral nanofluids for extra emergency cooling of overheated surfaces of powerful equipment in the event of the sudden onset of a boiling crisis.

Enhanced surface wettability and innate activity of an iron borate catalyst for efficient oxygen evolution and gas bubble detachment

2019 ◽  
Vol 7 (25) ◽  
pp. 15252-15261 ◽  
Author(s):  
Kamran Dastafkan ◽  
Yibing Li ◽  
Yachao Zeng ◽  
Li Han ◽  
Chuan Zhao
Keyword(s):  
Oxygen Evolution ◽  
Nickel Foam ◽  
Dip Coating ◽  
Surface Wettability ◽  
Gas Bubble ◽  
Iron Borate ◽  
Bubble Detachment ◽  
Enhanced Surface

Alternating dip-coating of iron borate on nickel foam provides surface wettability towards achieving a low-adhesion oxygen evolution electrode.

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